freeCodeCamp/curriculum/challenges/english/10-coding-interview-prep/rosetta-code/happy-numbers.md

id, title, challengeType, forumTopicId, dashedName

id	title	challengeType	forumTopicId	dashedName
594810f028c0303b75339ad1	Happy numbers	5	302280	happy-numbers

--description--

A happy number is defined by the following process:

Starting with any positive integer, replace the number by the sum of the squares of its digits, and repeat the process until the number equals 1 (where it will stay), or it loops endlessly in a cycle which does not include 1. Those numbers for which this process ends in 1 are happy numbers, while those that do not end in 1 are unhappy numbers.

--instructions--

Implement a function that returns true if the number is happy, or false if not.

--hints--

happy should be a function.

assert(typeof happy === 'function');

happy(1) should return a boolean.

assert(typeof happy(1) === 'boolean');

happy(1) should return true.

assert(happy(1));

happy(2) should return false.

assert(!happy(2));

happy(7) should return true.

assert(happy(7));

happy(10) should return true.

assert(happy(10));

happy(13) should return true.

assert(happy(13));

happy(19) should return true.

assert(happy(19));

happy(23) should return true.

assert(happy(23));

happy(28) should return true.

assert(happy(28));

happy(31) should return true.

assert(happy(31));

happy(32) should return true:.

assert(happy(32));

happy(33) should return false.

assert(!happy(33));

--seed--

--seed-contents--

function happy(number) {

}

--solutions--

function happy (number) {
  let m;
  let digit;
  const cycle = [];

  while (number !== 1 && cycle[number] !== true) {
    cycle[number] = true;
    m = 0;
    while (number > 0) {
      digit = number % 10;
      m += Math.pow(digit, 2);
      number = (number - digit) / 10;
    }
    number = m;
  }
  return (number === 1);
}